solid-architecture

SOLID & Clean Architecture

Single Responsibility (SRP)

• One module = one reason to change. If a file mixes UI rendering with business logic, data access with orchestration, or config with behavior — split it.
• Max 300 lines per file. Max 30 lines per function. Max 5 parameters (use options object beyond that).
• Template literals embedding >20 lines of CSS, JS, or HTML must be extracted to separate files.

Open/Closed (OCP)

• Prefer data-driven designs over per-variant functions. Use config maps + one generic function instead of N nearly-identical functions.
• Use handler/strategy maps (Record<EventType, Handler>) instead of switch statements with >5 cases.

Liskov Substitution (LSP)

• Subclasses/implementations must honor the contract of their parent. Never override a method to throw "not supported" — redesign the hierarchy instead.

Interface Segregation (ISP)

• No Record<string, unknown>, any, or object in public APIs. Define narrow, purpose-specific types.
• Use TypeScript generics (<T>) instead of loose types + inline as casts.

Dependency Inversion (DIP)

• Import from barrel exports (index.ts), not deep internal paths. Every public symbol must be re-exported from the package barrel.
• Use static import statements. Never use require() in TypeScript unless technically justified and documented.
• Depend on abstractions (interfaces/types), not concrete implementations, when crossing module boundaries.

Separation of Concerns

• View layer: layout and event binding only. No business logic, no data fetching.
• Service layer: orchestration, external calls, state mutations.
• Data layer: queries, I/O, serialization. No UI references.